P
US7323732B2ExpiredUtilityPatentIndex 84

MRAM array employing spin-filtering element connected by spin-hold element to MRAM cell structure for enhanced magnetoresistance

Assignee: MACRONIX INT CO LTDPriority: Mar 3, 2004Filed: Mar 3, 2004Granted: Jan 29, 2008
Est. expiryMar 3, 2024(expired)· nominal 20-yr term from priority
Inventors:HO CHIAHUALUNG HSIANG-LAN
G11C 11/1659G11C 11/1675G11C 11/161G11C 11/16
84
PatentIndex Score
9
Cited by
3
References
95
Claims

Abstract

An MRAM array having enhanced magnetoresistance includes a spin filtering element connected by a spin hold element to the MRAM cell structures. A spin filtering element may serve several MRAM cell structures, by connecting the spin filtering element to a series of MRAM cell structures by a spin hold wire, or a spin filtering element and a spin hold element may be formed as adjacent layers in each MRAM cell stack.

Claims

exact text as granted — not AI-modified
1. A MRAM construct, comprising a MRAM cell structure connected by a spin hold element to a spin filtering element. 
   
   
     2. The MRAM construct of  claim 1  wherein the MRAM cell structure comprises a GMR device. 
   
   
     3. The MRAM construct of  claim 1  wherein the MRAM cell structure comprises a MTJ device. 
   
   
     4. The MRAM construct of  claim 2  wherein the MRAM cell structure comprises at least two ferromagnetic layers separated by a conductor layer. 
   
   
     5. The MRAM construct of  claim 3  wherein the MRAM cell structure comprises at least two ferromagnetic layers separated by an insulator layer. 
   
   
     6. The MRAM construct according to  claim 1  wherein the spin filtering element includes a ferromagnetic material having a high magnetic polarization value. 
   
   
     7. The MRAM construct according to  claim 1  wherein the spin filtering element includes a Heusler alloy. 
   
   
     8. The MRAM construct according to  claim 7  wherein the Heusler alloy is a Mn based Heusler alloy. 
   
   
     9. The MRAM construct according to  claim 1  wherein the spin filtering element includes a Mn based Heusler alloy selected from the group consisting of NiMnSb and NiMnGa. 
   
   
     10. The MRAM construct according to  claim 7  wherein the Heusler alloy is an oxide based Heusler alloy. 
   
   
     11. The MRAM construct according to  claim 1  wherein the spin filtering element includes an oxide based alloy selected from the group consisting of Fe 3 O 4  and CrO 2 . 
   
   
     12. The MRAM construct according to  claim 1  wherein the spin filtering element includes a Mn based CMR material. 
   
   
     13. The MRAM construct according to  claim 12  wherein the spin filtering element includes a Mn based CMR material selected from the group consisting of La x Sr 1-x MnO 3  and Pr x Ca 1-x MnO 3 . 
   
   
     14. The MRAM construct according to  claim 1  wherein the spin filtering element includes a Mn based ferromagnetic material. 
   
   
     15. The MRAM construct according to  claim 14  wherein the Mn based ferromagnetic material of the spin filtering element comprises NiMnGa. 
   
   
     16. The MRAM construct according to  claim 14  wherein the Mn based ferromagnetic material of the spin filtering element comprises NiMnSb. 
   
   
     17. The MRAM construct according to  claim 1  wherein the spin filtering element includes an oxide based ferromagnetic material. 
   
   
     18. The MRAM construct according to  claim 17  wherein the oxide based ferromagnetic material of the spin filtering element comprises Fe 3 O 4 . 
   
   
     19. The MRAM construct according to  claim 17  wherein the oxide based ferromagnetic material of the spin filtering element comprises CrO 2 . 
   
   
     20. The MRAM construct according to  claim 1  wherein the spin hold element comprises a material having a high spin diffusion length. 
   
   
     21. The MRAM construct according to  claim 20  wherein the spin hold element comprises a material having a spin diffusion length at least about 100 nm. 
   
   
     22. The MRAM construct according to  claim 1  wherein the spin hold element comprises Bi. 
   
   
     23. The MRAM construct according to  claim 22  wherein the spin hold element comprises single-crystal Bi. 
   
   
     24. The MRAM construct according to  claim 22  wherein the spin hold element comprises poly-crystal Bi. 
   
   
     25. The MRAM construct according to  claim 1  wherein the spin hold element and the spin filtering element are adjacent layers in the MRAM cell structure, and the spin hold element comprises a conductive metal layer having a thickness less than the electron mean free path in the metal. 
   
   
     26. The MRAM construct of  claim 25  wherein the metal of the spin hold conductive metal layer is Cu. 
   
   
     27. The MRAM construct of  claim 26  wherein the spin hold Cu layer has a thickness in the range about 4 nm to about 10 nm. 
   
   
     28. The MRAM construct of  claim 25  wherein the metal of the spin hold conductive metal layer is Al. 
   
   
     29. The MRAM construct of  claim 28  wherein the spin hold Al layer has a thickness in the range about 4 nm to about 5 nm. 
   
   
     30. The MRAM construct according to  claim 1  wherein the MRAM cell structure comprises a MTJ system having first and second ferromagnet layers separated by a thin insulator, the ferromagnet layers having different coercivity fields. 
   
   
     31. The MRAM construct according to  claim 30  wherein the insulator comprises a material selected from the group consisting of Al 2 O 3 , AlN, AlON, Ga 2 O 3 , SrTiO 3 , HFO 2 , Ta 2 O 5 . 
   
   
     32. The MRAM construct according to  claim 30  wherein the first ferromagnet layer comprises a material different from that of the second ferromagnet layer. 
   
   
     33. The MRAM construct according to  claim 30  wherein the first ferromagnet layer and the second ferromagnet layer each comprise a material selected from the group consisting of a 3d transition ferromagnet material. 
   
   
     34. The MRAM construct of  claim 33  wherein the 3d transition ferromagnetic material is selected form the group consisting of Fe, Co, CoFe and CoFeNi. 
   
   
     35. The MRAM construct of  claim 30  wherein the first ferromagnet layer and the second ferromagnet layer each comprise a Heusler alloy. 
   
   
     36. The MRAM construct of  claim 35  wherein the Heusler alloy comprises a material selected from the group consisting of La x Sr 1-x MnO 3  and Pr x Ca 1-x MnO 3 . 
   
   
     37. The MRAM construct of  claim 30  wherein the first ferromagnet layer and the second ferromagnet layer each comprise an oxide based alloy. 
   
   
     38. The MRAM construct of  claim 37  wherein the oxide based alloy is selected from the group consisting of Fe 3 O 4  and CrO 2 . 
   
   
     39. The MRAM construct according to  claim 1  wherein the MRAM cell structure comprises a GMR system having first and second ferromagnet layers separated by a thin conductor, the ferromagnet layers having different coercivity fields. 
   
   
     40. The MRAM construct according to  claim 39  wherein the conductor comprises a material selected from the group consisting of Cu, Ag, Au, Ru, Cr. 
   
   
     41. The MRAM construct according to  claim 39  wherein the first ferromagnet layer comprises a material different from that of the second ferromagnet layer. 
   
   
     42. The MRAM construct according to  claim 39  wherein the first ferromagnet layer and the second ferromagnet layer each comprise a material selected from the group consisting of a 3d transition ferromagnet material. 
   
   
     43. The MRAM construct of  claim 42  wherein the 3d transition ferromagnetic material is selected form the group consisting of Fe, Co, CoFe and CoFeNi. 
   
   
     44. The MRAM construct of  claim 39  wherein the first ferromagnet layer and the second ferromagnet layer each comprise a Heusler alloy. 
   
   
     45. The MRAM construct of  claim 43  wherein the Heusler alloy comprises a material selected from the group consisting of La x Sr 1-x MnO 3  and Pr x Ca 1-x MnO 3 . 
   
   
     46. The MRAM construct of  claim 39  wherein the first ferromagnet layer and the second ferromagnet layer each comprise an oxide based alloy. 
   
   
     47. The MRAM construct of  claim 46  wherein the oxide based alloy is selected from the group consisting of Fe 3 O 4  and CrO 2 . 
   
   
     48. The MRAM construct according to  claim 30  wherein the MRAM cell structure comprises a spin-valve MTJ. 
   
   
     49. The MRAM construct according to  claim 32  wherein the spin-valve MTJ comprises a free ferromagnetic layer and a pinned ferromagnetic layer and a pinning layer. 
   
   
     50. The MRAM construct according to  claim 49  wherein the pinning layer comprises an antiferromagnetic material. 
   
   
     51. The MRAM construct according to  claim 49  wherein the pinning layer comprises a Mn based material. 
   
   
     52. The MRAM construct according to  claim 51  wherein the Mn based material is selected from the group consisting of IrMn and FeMn. 
   
   
     53. The MRAM construct according to  claim 49  wherein the pinning layer comprises a synthetic antiferromagnetic multilayer. 
   
   
     54. The MRAM construct according to  claim 53  wherein the synthetic antiferromagnetic multilayer comprises layers selected from the group consisting of CoFe/Ru/CoFe and Co/Ru/Co. 
   
   
     55. The MRAM construct according to  claim 49  wherein the pinning layer comprises a mixed multilayer comprising a synthetic antiferromagnetic material and an antiferromagnetic material. 
   
   
     56. The MRAM construct according to  claim 55  wherein the mixed multilayer comprises layers selected from the group consisting of IrMn/CoFe/Ru/CoFe and FeMn/Co/Ru/Co. 
   
   
     57. The MRAM construct according to  claim 49  wherein the pinning layer comprises a permanent magnet material. 
   
   
     58. The MRAM construct according to  claim 49  wherein the permanent magnet material is selected from the group consisting of SmCo and SmFeCo. 
   
   
     59. The MRAM construct according to  claim 30  wherein the MRAM cell structure comprises a pseudo-spin valve MTJ. 
   
   
     60. The MRAM construct according to  claim 59  wherein the MRAM cell structure comprises a soft ferromagnetic layer and a hard ferromagnetic layer, wherein the coercivity of the hard ferromagnetic layer is greater than the coercivity of the soft ferromagnetic layer. 
   
   
     61. The MRAM construct of  claim 60  wherein the soft ferromagnetic layer comprises a material selected from the group consisting of NiFe, Co and NiFeCo. 
   
   
     62. The MRAM construct of  claim 60  wherein the hard ferromagnetic layer comprises a material selected from the group consisting of CoFe and Co. 
   
   
     63. The MRAM construct of  claim 30  wherein the MRAM cell structure comprises a MTJ comprising a granular material. 
   
   
     64. The MRAM construct of  claim 63  wherein the distance between grains of ferromagnetic material is in a range about 100 Å to about 300 Å. 
   
   
     65. The MRAM structure of  claim 63  wherein the granular material is selected from the group consisting of Fe-Al 2 O 3 , Fe-SiO 2 , Co-SiO 2 . 
   
   
     66. The MRAM construct according to  claim 39  wherein the MRAM cell structure comprises a spin-valve GMR. 
   
   
     67. The MRAM construct according to  claim 66  wherein the spin-valve GMR comprises a free ferromagnetic layer and a pinned ferromagnetic layer and a pinning layer. 
   
   
     68. The MRAM construct according to  claim 67  wherein the pinning layer comprises an antiferromagnetic material. 
   
   
     69. The MRAM construct according to  claim 67  wherein the pinning layer comprises a Mn based material. 
   
   
     70. The MRAM construct according to  claim 69  wherein the Mn based material is selected from the group consisting of IrMn and FeMn. 
   
   
     71. The MRAM construct according to  claim 67  wherein the pinning layer comprises a synthetic antiferromagnetic multilayer. 
   
   
     72. The MRAM construct according to  claim 71  wherein the synthetic antiferromagnetic multilayer comprises layers selected from the group consisting of CoFe/Ru/CoFe and Co/Ru/Co. 
   
   
     73. The MRAM construct according to  claim 67  wherein the pinning layer comprises a mixed multilayer comprising synthetic antiferromagnetic material and an antiferromagnetic material. 
   
   
     74. The MRAM construct according to  claim 73  wherein the mixed multilayer comprises layers selected from the group consisting of IrMn/CoFe/Ru/CoFe and FeMn/Co/Ru/Co. 
   
   
     75. The MRAM construct according to  claim 67  wherein the pinning layer comprises a permanent magnet material. 
   
   
     76. The MRAM construct according to  claim 67  wherein the permanent magnet material is selected from the group consisting of SmCo and SmEeCo. 
   
   
     77. The MRAM construct according to  claim 39  wherein the MRAM cell structure comprises a pseudo-spin valve GMR. 
   
   
     78. The MRAM construct according to  claim 77  wherein the MRAM cell structure comprises a soft ferromagnetic layer and a hard ferromagnetic layer, wherein the coercivity of the hard ferromagnetic layer is greater than the coercivity of the soft ferromagnetic material. 
   
   
     79. The MRAM construct of  claim 78  wherein the soft ferromagnetic layer comprises a material selected from the group consisting of NiFe, Co and NiFeCo. 
   
   
     80. The MRAM construct of  claim 78  wherein the hard ferromagnetic layer comprises a material selected from the group consisting of CoFe and Co. 
   
   
     81. The MRAM construct of  claim 39  wherein the MRAM cell structure comprises a GMR comprising a granular material. 
   
   
     82. The MRAM construct of  claim 81  wherein the distance between grains of ferromagnetic material is in a range about 100 Å to about 300 Å. 
   
   
     83. The MRAM structure of  claim 81  wherein the granular material is selected from the group consisting of Fe-Al 2 O 3 , Fe-SiO 2 , Co-SiO 2 . 
   
   
     84. The MRAM structure of  claim 39  wherein the GRM system comprises a periodic multilayer structure, alternating a ferromagnetic material with a nonferromagnetic material. 
   
   
     85. The MRAM structure of  claim 84  wherein the multilayer structure comprises (NiFe/Cu) n . 
   
   
     86. A MRAM array comprising the MRAM construct of  claim 1 . 
   
   
     87. An MRAM construct comprising a plurality of MRAM cell structures, and including a spin filtering element connected to the plurality of MRAM cell structures by a spin hold wire adjacent a first ferromagnetic layer on the MRAM cell structures. 
   
   
     88. The MRAM construct of  claim 87  wherein the spin hold wire comprises Bi. 
   
   
     89. An MRAM construct comprising a plurality of MRAM cells, each MRAM cell comprising a MRAM cell structure, a spin hold layer adjacent the MRAM cell structure, and a spin filtering layer adjacent the spin hold layer. 
   
   
     90. The MRAM construct of  claim 89  wherein the spin hold layer comprises Bi. 
   
   
     91. The MRAM construct of  claim 89  wherein the spin hold layer comprises a layer of a conductive metal, the layer having a thickness less than the electron mean free path in the metal. 
   
   
     92. The MRAM construct of  claim 91  wherein the conductive metal layer comprises Cu. 
   
   
     93. The MRAM construct of  claim 92  wherein the Cu layer has a thickness in the range about 4 nm to about 10 nm. 
   
   
     94. The MRAM construct of  claim 91  wherein the layer comprises Al. 
   
   
     95. The MRAM construct of  claim 94  wherein the Al layer has a thickness in the range about 4 nm to about 5 nm.

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